In microprocessing for manufacturing a semiconductor device or a FPD (Flat Panel Display) using plasma, it is very important to control a temperature or a temperature distribution of a processing target substrate (a semiconductor wafer, a glass substrate, etc.) as well as to control a plasma density distribution on the processing target substrate. If the temperature control of the substrate is not performed appropriately, uniformity of process characteristics as well as substrate surface reaction may not be achieved. As a result, a decrease of a production yield of semiconductor devices or display devices may occur.
In general, a mounting table or susceptor, which mounts thereon a processing target substrate within a vessel of a plasma processing apparatus (particularly, a capacitively coupled plasma processing apparatus), has a function as a high frequency electrode that applies a high frequency power into a plasma space, a function as a holder that holds thereon the substrate by electrostatic attraction or the like; and a function as a temperature controller that controls the temperature of the substrate to a certain temperature by heat transfer. As for the temperature control function, it is required to appropriately correct a heat transfer characteristic distribution of the substrate affected by non-uniform radiant heat from plasma or a vessel wall, or a heat distribution affected by a substrate supporting structure.
Conventionally, in order to control the temperature of the susceptor or the substrate, a heater structure is widely employed. In this structure, a heating element configured to generate heat by applying an electric current is provided in the susceptor, and Joule heat generated by the heating element is controlled. When using such a heater structure, however, a part of a high frequency power applied to the high frequency electrode of the susceptor from a high frequency power supply might be easily introduced into a heater power feed line through the heating element. If a high frequency noise reaches a heater power supply through the heater power feed line, operation or performance of the heater power supply might be deteriorated. Further, if a high frequency current flows in the heater power feed line, the high frequency power would be wasted. Typically, to solve these problems, a filter configured to attenuate or block the high frequency noise flowing from the heating element embedded in the susceptor is provided on the heater power feed line.
The present applicant describes, in Patent Document 1, a plasma processing apparatus in which an air core coil having large inductance is provided at an upstream end of such kind of filter, and the air core coil is accommodated in a conductive casing provided at the vicinity of (typically, below) a susceptor. In this plasma processing apparatus, when a single high frequency power equal to or lower than about 13.56 MHz is applied to a high frequency electrode within the susceptor, the filter with the air core coil configured as mentioned above may be operated effectively. Accordingly, while allowing a large amount of a heater current equal to or larger than about 30 A to flow in a heater power feed line, a high frequency noise equal to or lower than about 13.56 MHz can be blocked effectively, securely and stably.
Further, the present applicant also describes, in Patent Document 2, a technique for improving the performance of a filter configured to block a high frequency noise having a high frequency that flows into a heater power feed line from a susceptor within a processing vessel of a plasma processing apparatus. This filter technique uses a regular multiple parallel resonance characteristic of a distributed constant line. Accordingly, even when a high frequency power having a high frequency (e.g., about 27 MHz) is applied to a high frequency electrode within the susceptor as well as in case that a high frequency power having a relatively low frequency is applied, the filter is capable of blocking the high frequency noise with only one air core coil, and, thus, the only one coil needs to be accommodated in a housing of the filter.
Patent Document 1: Japanese Patent Laid-open Publication No. 2008-198902
Patent Document 2: Japanese Patent Laid-open Publication No. 2011-135052
However, in the conventional plasma processing apparatus using the filter configured to block a high frequency noise introduced into the heater power feed line via the high frequency electrode and the heating element within the susceptor, a layout of the filter or an arrangement of the heater power feed line directly under the susceptor may have adverse influence on electron density distribution on the susceptor or in-plane uniformity of process characteristics as well as on a frequency-impedance characteristic of the filter.